227
FXUS02 KWBC 231843
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
143 PM EST THU JAN 23 2025
VALID 12Z SUN JAN 26 2025 - 12Z THU JAN 30 2025
..OVERVIEW
IT IS STILL THE CASE THAT THE START OF THE PERIOD ON SUNDAY WILL
FEATURE AN UPPER LEVEL CLOSED LOW DIVING SOUTHWARD ALONG THE
CALIFORNIA COAST, AND ONLY VERY SLOWLY MOVING EASTWARD WITH TIME
NEXT WEEK. THIS SHOULD BRING BENEFICIAL PRECIPITATION TO PARTS OF
SOUTHERN CALIFORNIA THAT HAVE BEEN DEALING WITH DEVASTATING
WILDFIRES. ORGANIZED RAINS/TERRAIN SNOWS SHOULD MAKE THEIR WAY
DOWNSTREAM INTO THE SOUTHWEST AS WELL. MEANWHILE, NORTHERN STREAM
MEAN TROUGHING, AND REINFORCING SHORTWAVES WILL CROSS FROM THE
NORTHERN PLAINS INTO THE GREAT LAKES AND NORTHEAST INTO NEXT WEEK.
MODERATE TO LOCALLY HEAVY RAINFALL WILL DEVELOP TO THE SOUTH ACROSS
THE LOWER MISSISSIPPI VALLEY SUNDAY AND MONDAY AS A SLOW MOVING
FRONTAL BOUNDARY MOVES THROUGH THE REGION. ADDITIONAL FRONTAL WAVE
GENESIS OVER THE SOUTHERN PLAINS INTO MID-LATER NEXT WEEK GIVEN
SOUTHWEST UPPER LOW SLOW APPROACH MAY AGAIN INCREASE LEAD RETURN
FLOW AND EMERGING RAINFALL TO MONITOR. THE SIGNAL FOR AN EMERGING
PERIOD OF HEAVY RAINFALL IS GROWING, BUT PLACEMENT REMAINS QUITE
UNCERTAIN AT THIS TIME.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL AND ENSEMBLE FORECAST SPREAD CONTINUES TO SLOWLY IMPROVE
OVER THE PAST FEW RUN CYCLES, BOLSTERING FORECAST CONFIDENCE
THROUGH MUCH OF THE UPCOMING MEDIUM-RANGE FORECAST PERIOD. THIS
FAVORABLE TREND CONTINUED WITH THE LATEST 12 UTC CYCLE.
ACCORDINGLY, A BLENDED GUIDANCE FORECAST STRATEGY THAT LEANS MORE
ON THE MODELS SUNDAY-TUESDAY, AND THEN ON THE ENSEMBLE MEANS AT
LONGER TIME FRAMES WILL TEND TO MITIGATE NUMEROUS LINGERING
SMALLER SCALE DIFFERENCES AS CONSISTENT WITH INDIVIDUAL
PREDICTABILITY. THIS PLAN ACTS TO MAINTAIN MAXIMUM WPC PRODUCT
CONTINUITY AS MOSTLY IN LINE WITH THE NATIONAL BLEND OF MODELS.
..WEATHER/HAZARDS HIGHLIGHTS
WPC CONTINUITY HAS BEEN WELL MAINTAINED FOR OVERALL MESSAGING ON
THE MAIN UPCOMING WEATHER/HAZARDS HIGHLIGHTED OVERNIGHT (BELOW):
THE SLOW MOVING UPPER LOW THROUGH CALIFORNIA ON SUNDAY WILL
CONTINUE TO ALLOW FOR MUCH NEEDED RAIN TO SOUTHERN CALIFORNIA. EVEN
THOUGH QPF AMOUNTS ARE NOT TOO HIGH, GIVEN SENSITIVITY ESPECIALLY
IN FRESH BURN SCAR LOCATIONS, IT MAY NOT TAKE MUCH TO CAUSE
FLOODING CONCERNS. FOR THIS REASON, A SMALL MARGINAL RISK WAS ADDED
TO PARTS OF SOUTHERN CALIFORNIA ON THE DAY 4 EXCESSIVE RAINFALL
OUTLOOK. MODEST SNOWS ARE POSSIBLE ACROSS THE TERRAIN OF SOUTHERN
CALIFORNIA, WITH RAIN AND MOUNTAIN SNOW INTO PARTS OF THE SOUTHWEST
AS WELL. A TIGHTENED GRADIENT BEHIND THE COLD FRONT DROPPING SOUTH
MAY PRODUCE SOME GUSTY WINDS ALONG PARTS OF THE ROCKIES LATE THIS
WEEK AND CALIFORNIA AND NEVADA ON SATURDAY WITH OFFSHORE FLOW AND
MODESTLY FAVORABLE FIRE WEATHER CONDITIONS POSSIBLE AGAIN BEHIND
THE UPPER LOW NEXT WEEK TO KEEP AN EYE ON.
FARTHER EAST, GULF MOISTURE WILL INTERACT WITH A FRONT APPROACHING
THE LOWER MISSISSIPPI VALLEY TO TENNESSEE AND OHIO VALLEYS BY THIS
COMING WEEKEND/EARLY NEXT WEEK. LATEST GUIDANCE CONTINUES TO SHOW
HEAVY RAINFALL TOTALS OVER PARTS OF THE SOUTHERN U.S., WITH THE
POTENTIAL FOR HEAVY RAIN AND THUNDERSTORMS ON SUNDAY ACROSS
SOUTHEAST TEXAS AND THE LOWER MISSISSIPPI VALLEY. A MARGINAL RISK
WAS CARRIED INTO THE NEW DAY 4/SUNDAY EXCESSIVE RAINFALL OUTLOOK
FROM EASTERN TEXAS INTO MISSISSIPPI WHERE STORMS MAY TRAIN ALONG A
SLOW MOVING FRONTAL BOUNDARY. SOME SNOW OR A WINTRY MIX IS
POSSIBLE ON THE NORTHERN SIDE OF THIS PRECIPITATION SHIELD MAINLY
OVER THE OHIO VALLEY, SOUTH-CENTRAL APPALACHIANS, AND POSSIBLY THE
TENNESSEE VALLEY AND VICINITY. PRECIPITATION MAY SPREAD TOWARDS THE
EAST COAST EARLY NEXT WEEK AS THE FRONTAL SYSTEM PROGRESSES WITH
SOME RAINFALL REDEVELOPMENT ACROSS THE SOUTHERN PLAINS AND LOWER
MISSISSIPPI VALLEY AS WELL. THIS SIGNAL IS INCREASING WITH
DEVELOPMENT OF AN ORGANIZED FRONTAL WAVE WITH SOUTHWEST UPPER
SYSTEM APPROACH, BUT RAINFALL FOCUS AND AXIS REMAINS UNCERTAIN.
MUCH OF THE EAST SHOULD FINALLY BE BACK UP TOWARDS NORMAL
TEMPERATURES EARLY NEXT WEEK, THOUGH READINGS A FEW DEGREES BELOW
NORMAL ARE POSSIBLE ACROSS THE SOUTHEAST. ANOMALOUSLY COLD
TEMPERATURES WILL ALSO DEVELOP IN THE HIGH PLAINS, ROCKIES, AND
MUCH OF THE WEST UNDER THE INFLUENCE OF UPPER TROUGHING. THE
COLDEST ANOMALIES WILL BE IN THE HIGH PLAINS AND ROCKIES TO
SOUTHERN HIGH PLAINS WHERE HIGH TEMPERATURES COULD BE 10-20 DEGREES
BELOW NORMAL. LATE PERIOD RIDGING OVER THE NORTHERN TIER COULD
ALLOW TEMPERATURES TO RISE ABOVE NORMAL NEXT WEEK, GRADUALLY
SHIFTING SOUTH AND EAST WITH TIME.
SANTORELLI/SCHICHTEL
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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